Solve the all parts of given problem:
Problem: A 4 mev photon brings about pair production in a piece of material. assume the electron and positron pair move in opposite direction with equal speed.
Part A: What is the kinetic energy of the positron?
Part B: What is the speed of the positron as measured by an observer in the lab?
I need help to find the speed of the positron as measured by an observer in the lab.